Motion simulators are often used for the purpose of training, education, testing and entertainment. These devices include flight simulators, amusement rides and the like, and may also have application in the developing field of virtual reality.
Such motion simulators typically have a movable platform, a stationary base, and a servo-controlled articulation mechanism arranged between the platform and the base for selectively articulating the platform in a manner so as to simulate the motion of a vehicle. The perception that the passengers are in a vehicle may be further enhanced by visual and audible displays.
Depending upon the particular motion to be simulated, the platform motions may be rapid (as required), but are preferably smooth (i.e., without abrupt steps or bumps due to friction). Moreover, where human passengers are expected to ride on the platform, special demands are placed on performance and safety features. If the actuation system fails, for whatever reason, care must be taken to insure the continued safety of the passengers.
In most prior motion simulation systems, regardless of size or degrees of freedom, the actuation mechanism has typically consisted of electrohydraulic servoactuators. The state of this art has advanced markedly over the years with solutions of various performance and safety problems. For example, actuator friction problems have been substantially reduced through the use of special seals and hydrostatic bearings. End-of-stroke actuator snubbing has been implemented with piston-related flow restrictions. Pressurized accumulators have provided supplemental hydraulic energy for controlled return to the loading position. Solenoid-operated valves, controlled by electrical failure sensors, have blocked or isolated servovalves, and have selectively connected suitable bypasses across an actuator to allow for a slow "crash" and a safe "abort" condition. These features are largely carry-overs from other hydraulic applications, and are inherently available in use of fluid control.
While hydraulic servoactuators provide excellent motion control performance, they do have a number of disadvantages. These range from high maintenance due to leakage of environmentally-unfriendly and flammable fluids, to problems associated with contamination of the serviced fluid(s) and the undesired closure of small restrictive orifices, to low energy efficiency with the attendant problem of heat dissipation. In addition, a typical hydraulic system installation usually requires the costly and unnecessary construction of a separate pump room to house the pumping equipment and to contain the associated heat, noise and hazardous materials.